Auxiliary lock with an extensible device

Claim 1

A length-adjustable auxiliary lock comprising a main cylinder having a front end provided with a face plate and a back end, a dead bolt in the main cylinder, a linking plate extending out the back end of the main cylinder, a cylindrical post on the linking plate having a longitudinal axis and extending into a bore in the dead bolt, a helical track formed on the post and a pin assembly on the dead bolt engaging the track whereby rotation of the linking plate about the longitudinal axis of the post moves the linking late lengthwise relative to the dead bolt to adjust the length of the lock, an extending cylinder surrounding the main cylinder, an assembling plate carried by the extending cylinder and secured to the linking plate at the back of the main cylinder, whereby rotation of the assembling plate and the extending cylinder relative to the main cylinder thereby effects rotation of the linking plate to adjust the length of the lock, the main cylinder having a peripheral wall defining a depressable tongue, a locating projection on said tongue and front and back locating apertures in the extending cylinder for receiving said projection in respective extended and contracted positions of the lock, the extending cylinder and said projection cooperating to depress said tongue when the extending cylinder is moved between said positions, and the dead bolt being formed with a flat surface which is engaged by the tongue when depressed to prevent rotation of the dead bolt.